In general, a fuel cell is a type of device configured to generate electricity by electrochemically reacting chemical energy of the fuel in a fuel cell stack to be converted into electrical energy. The fuel cell supplies a power for industry, family use, and for driving a vehicle, and is applied to an electric/electronic product having a substantially small size, and recently, has been applied to a vehicle.
A fuel cell system disposed within the vehicle includes a fuel cell stack configured to generate an electrical energy, a fuel supplying device configured to supply a fuel (hydrogen) to the fuel cell stack, an air supplying device configured to supply oxygen in air which is an oxidizer required for an electrochemical reaction, to the fuel cell stack, a thermal management system (TMS) configured to remove reaction heat of the fuel cell stack to be discharged to the exterior of the system and adjust an operation temperature of the fuel cell stack In the fuel cell system having the above-described configuration, electricity is generated by the electrochemical reaction using the hydrogen which is the fuel and the oxygen in the air, and water and heat are discharged as reaction by-products.
Since the heat is generated as the reaction by-product in the fuel cell system, a device for cooling the stack is essential to prevent an increase in temperature of the stack In addition, since the fuel cell system is used to maintain cold engine start properties, the thermal management system (TMS) is significantly important. It is well known in the art that cooling water of a TMS line serves as a cooling medium which cools the stack and simultaneously serves as a heating medium which performs rapid thawing on the stack to thereby be rapidly heated by a heater to be supplied to the stack during the cold engine start.
Since some of the cooling water always flows in the existing fuel cell for a vehicle, flow loss occurs, and therefore, during hot weather, an amount of the cooling water is insufficient, and as a result, there is a limitation in a current in a vehicle due to the cooling water at a high temperature which decreases an output, such that fuel efficiency is deteriorated.